These functions have been seperate for all the reasons and in the ways folks have already stated.
Perhaps the question should be: are these things seperate - or is there an expectation that they should be seperate - in the minds of the people an organization is trying to reach?
I believe people looking in on an organization expect some continuity.
Don't take my comment to mean I think continuity should be limited to a "top down" or central focus. The contemporary paradigm includes 2.0.